Safety detonator



Patented Sept. 26, 1933 PATENT OFFICE SAFETY DETONATOB Sylvester B.Large, Tamaqua, Pa., assignor to Atlas Powder Company, Wilmington, Del.,a corporation of Delaware No Drawing. Application August 29, 1932 SerialNo. 630,975

21Claims.

My invention relates to improvements in detonators, such as are used forinitiating charges of explosives. It is applicable to both electric andsafety fuse types of both simple and com pound detonators.

Its object is the production and use of new and improved types ofdetonators, characterized by excellent and reliable detonatingefliciency, by low cost, and by being safer for manufacture and use thanany detonators having sensitive explosives, such as fulminate, azide,diazodinitrophenol and the like, as ingredients of the main charge orcharges, thereof.

A further object is the reliable, eflicient and practical initiation ofthese safer types of detonators, whose main charge or charges are freeof any explosive as sensitive to friction and impact as mercuryfulminate, azide, etc.

Further objects and advantages will be evident from the followingdescription of my invention.

Where referred to in this specification and appended claims, the termprimary detonator composition means the material used as the entireexplosive charge in so called simple or singlecharge detonators; or thatused as the primary or top explosive charge in so called compound"detonators, in which are employed explosive base charges, usually of thenon-primary detonating type.

Various kinds of what I term safety types of primary detonatorcompositions have been proposed for use in various types of detonators.These safety types of primary detonator compositions are characterizedor defined as those that are free of any explosive ingredient which isas sensitive to friction and impact as are any of the group ofexplosives exemplified by mercury fulminate, lead azide,diazodinitrophenol, etc. Examples of these safety types of primarydetonator compositions are: (1) solid nitration products of polyhydricalcohols of the general formula CnHn+2(OH) n (as nitrodulcite,nitromannite, etc.) alone or admixed with various propor- 5 tions ofother solid explosives, materially less sensitive than fulminate ofmercury, lead azide and the like (examples of such other solidexplosives being tetryl, nitrolactose, nitropentaerythrite, etc.);primary detonator compositions of this type having been disclosed in mycopending applications Nos. 502,559, 502,560, and 575,929; (2)

solid disaccharide nitric esters (as nitrolactose) alone or admixed withvarious proportions of other solid explosives, materially less sensitivethan fulminate of mercury, lead azide and the to a confined safety typeof primary detonator like, as disclosed in my copending application No.575,930; etc.

In adapting these so-called safety types of primary detonatorcompositons for practical use in detonators, two chief requisites areinvolved, namely; (1) they must be adequately confined and (2) they mustbe adequately initiated by effective ignition. The first requisite orthat of adequate confinement may easily be fulfilled by the use, forexample, of a perforated inner capsule, pressed upon the said safetytype of primary detonator compositon in a shell, in a way well known inthe manufacture of detonators and as shown in my copending applicatonSerial No. 502,560, the shell being preferably of relatively highstrength for best and most reliable results, as for example a gildngmetal shell having a wall thickness of about ten thousandths of an inch.By the term confining means, as used in the accompanying claims, I meanto include all the confining media of the primary charge, i. e., eitherthe confining shell or both the shell and auxiliary confining element,as a capsule, if and when the latter is used in the detonator. One meansof fulfilling the second requisite or that of effective ignition is bythe employment of a preformed fuse-head, in accordance with the methoddisclosed in my copending application Serial No. 502,560, severalelectric types of which are available and well known. This methodaccordingly provides an adequate, readily available, electricalmeans forinitiating detonators embodying safety types of primary detonatorcompositions; whereas, in contradistinction thereto, ordinary availabletypes of safety fuse are not adequate for the initiation of detonatorsof this type, due to the insufiicient heat or insufiicient combinationof heat and force provided therewith. It is accordingly very essentialto the art of fabricating practical detonators, wherein the safety typesof primary detonator compositions are employed, to provide an adequatemeans of initiation, whereby the ordinary safety fuse method of firingmay be used where desirable. My present invention fulfills this needand, when embodied in detonators of the said type, renders them suitablewith ordinary and readily available types of safety fuse as well as withelectrically heated bridge wire.

Broadly, my invention consists of the employm ment of a charge ofinflammable defiagrating material of such character and in such amountthat it will convey effective ignition from either safety fuse orelectrically heated bridge-wire initiation u recognized but controllablefactor.

composition, without premature injury to the confining medium or mediaof the detonator.

My invention is largely based upon the important discovery that theproper functioning of a safety type of primary detonator composition ina detonator, is dependent upon a hitherto un- This novel factor residesin the prevention of the destruction, injury or disturbance of theconfining media of a detonator, (embodying a confined primary charge ofsafety primary detonator composition) prior to the detonation of thesaid primary charge thereof. The extreme importance of this factor willbe evident from the illustrative examples of unsuitable ignition media,shown below.

I have found, for example, that the flame durations and temperatures ofcertain types of ignition media are unsuitable, because they tend tosoften, fuse and even burn through the confining media i. e., the shellsand/or inner capsules of the detonators, before the safety type ofprimary detonator composition is able to advance from ignition todetonation, during which period it is very essential to have theconfining media quite intact.

In such cases, the proper functioning of a detonator, embodying asafety" type of primary detonator composition, is rendered veryuncertain, due to the impaired confinement and to the very objectionablephenomenon of having the main explosives charge, (surrounding thedetonator and which the detonator is to set off or detonate) becomingignited, from the excessive heat of the said types of ignition media,before its detonation can be effected. Premature ignition of thesurrounding explosive involves many important disadvantages as forexample (1) the ejection of the detonator from the explosive by theforce of the flame of either the ignition medirim of the detonator orthe flame of the ignited surrounding explosive or both, (2) thelikelihood of dangerous hang-fires, (3) the generation of toxic gases,(4) the reduction of blasting efliciency, (5) the likelihood of ignitinginflammable gases and dusts in mines, etc. Exemplary types of ignitionmedia, embodying the above difiiculties, are compositions such asthermite; pyrotechnics whose fuels comprise excessive amounts ofpowdered magnesium, powdered aluminum or similar, very high heatproducing material; and the like.

The following composition is an example of the objectionably hot type,the many disadvantages of which are described above: 58% barium nitrate,29% magnesium powder and 13% lead hypophosphite. Ignition media,consisting of variously pressed charges of this mixturein amountsranging from .075 grain to .25 gram when employed in detonatorsembodying, for example, gilding metal shells and inner capsules, basecharges of tetryl, and primary charges of nitromannite, almostinvariably burn through the side walls of the shells prior to thedetonation of the detonators; resulting in unreliable functioning, asindicated by lead-plate tests, besides the preignition of many types ofsurrounding explosives, in a majority of instances. For example, out ofa group of fifteen attempts to detonate 60% nitroglycerine dynamite withdetonators of this exemplary type, the dynamite was pre-ignited in 66%%of the trials and in 26%% of the trials the detonators were blown clearof the dynamite charges by the force of the flame of the ignitionmedium, ignited dynamite or both; the dynamite continuing to burninstead of detonating.

sensitized in such a way as to make them pro- I from zero up to about1300 lbs. per square inch,

Further, in other exemplary cases, I have found ignition media, whichare prone to detonate upon being ignited in'the confines of a detonator,to yield variable and unreliable results, in conjunction with primarycharges of safety" types of primary detonator compositions. In suchcases, the confinement is prematurely shattered, prior to. theadvancement of the primary charge of safety" primary detonatorcomposition from ignition to detonation; thereby interfering with itsproper functioning. This effect may best be observed in compoundtypedetonators, having base charges of non-primary types of explosives; thereduced efliciency of the primary charge resulting in the failure of thebase charge to detonate, in spite of the fact thatthe same kind ofdetonators may be consistently completely detonated by means of types ofignition media, which avoid'premature injury of the confining media, inaccordance with my invention. Such materials, as for example, mercuryfulminate, fulminatechlorate, etc., which advance from ignition todetonation, at very rapid rates, even in small quantities, aretherefore, unsuitable, unless degressive burning or defiagrating insteadof detonating materials, in the quantities required for ignition media.An illustration of this is a composition consisting of 65% mercuryfulminate, 25% litharge and 10% antimony sulphide, whose brisance isinsufficient, in small quantities, to impart detonation to nitromannitecap charges confined under an inner capsule, but, nevertheless, detonatewith sufiicient force to so injure the confining media (shell and innercapsule) that the said nitromannite charges will not advance fromignition to detonation with sufficient efficiency to consistentlyinitiate detonator base charges of tetryl and the like.

In contradistinction to ignition media, which prematurely injure theconfining media, examples of which are described above, I have foundnon-detonating, progressive burning ignition media, whose flametemperatures and durations are such that they will effectively ignitesafety types of primary detonator compositions, when confined indetonator assemblies, without melting shattering or otherwiseprematurely injuring the confining media, to be entirely satisfactoryand practical. Ignition media, of this satisfactory type, are embodiedin various types of progressive burning or defiagrating compositions;various amounts of which are suitable, depending upon the heat and gasproduced by and the speed of burning of the defiagrating material in theconfines of the detonator assembly, together with the strength, heatresistance, and heat conductivity of the confining medium or media ofthe detonator assembly.

For instance, a deflagrating material exemplified by composition A,consisting of a mixture of 74% selenium dust and 26% barium peroxide,ignition charges of which evolve very little or no gaseous products ofdefiagration and insufficient developed heat to injure the detonatorshells and/or inner capsules, is quite flexible as to the maximumamounts that may be satisfactorily used as ignition media in detonatorsembodying confined charges of safety types of primary detonatorcompositions; the limiting factor, in this case, being the amountsrequired to develop suflicient heat to effectively ignite the said primary charges. In the case of composition A, about .4 gram or largeramounts, when pressed are suitable as ignition media for detonatorsembodying nitromannite and the like, as the primary charges thereof, inaccordance with my invention, in conjunction with confining media ofmaterials about as or more heat resistant than gilding metal.

As for the opposite extreme, involving defiagrating compositions,exemplified by composition Bcons'xsting of a mixture of 40% groundnitrocellulose smokeless powder, 20% potassium chlorate and 40%sulphocyanate, which are relatively fast burning and evolve considerablegaseous products of deflagration, the amounts used as the ignition mediamust be sufficiently small to prevent the bursting of the detonatorshell prior to the efiective ignition of the safety type of primarycharge; the gases, in this case, being generated in too great a volumeand at too rapid a rate for them to be vented past the crimped safetyfuse sumciently fast to avoid building up a pressure to the burstingpoint of the confining detonator shell. The amount of gas produced musttherefore be limited by limiting the amounts of composition of the Btype used as the ignition media. In the particular case of compositionB, I have found amounts ranging from .04 gram to .08 gram, pressed fromzero up to about 2600 lbs. per square inch, to be suitable as ignitionmedia for detonators embodying nitromannite, nitrodulcite, nitrolactose,and the like as the primary charges thereof, in accordance with myinvention, in conjunction with confining media of conventionalthicknesses of materials about as strong or stronger than gilding metal.

Between these two extreme types, represented by compositions A'and B, itwill readily be seen that there are many other compositions havingcombinations of intermediate characteristics, which are suitable inintermediate amounts, for use in accordance with my invention.Composition C, for example, consisting of 25% tetryl, 10% magnesiumpowder, 40% barium nitrate and 25% lead hypophosphite, deflagrates andevolves gas at a sufficiently moderate rate with sufficient evolution ofheat to efl'ectively initiate primary detonator charges of nitromannite,to be satisfactory for use, in accordance with my invention, inquantities varying from about .15 gram to about .25 gram, pressed fromzero up to about 2600 lbs. per square inch, under which conditionsinsuflicient heat and/or pressure is evolved to injure shells and innercapsules of conventional thickness, of materials about as or more heatresistant and/or stronger than gilding metal.

It is to be understood that my invention is not limited to the aboverecited examples of suitable ignition media but that it includes withinits purview all equivalents thereof, a large number of which can beformulated and adapted in accordance with my invention. Within this widerange there are certain ignition media that are better suited thanothers. For example, for detonators to be fired by safety fuseinitiation, I prefer to employ ignition media that are relatively low inhygroscopicity, readily pressed into a form that will not easily bedislodged with ordinary handling, readily ignited by the spit ofordinary safety fuse-even in the pressed state, sufficiently small inmagnitude to be economical, relatively insensitive to friction, etc.

Likewise, for example, for detonators to be fired by electrically heatedbridge-wireinitiation, I prefer to employ ignition media that arereadily ignited by ordinary types of electrically heated bridge-wires inthe loose state, relatively low in sensitivity and hygroscopicity, etc.7

Preferred types of inflammable compositions, for use as ignition media,in accordance with my invention, usually consist of an oxygen deliveringsubstance and a fuel; with orwithout an inflammability sensitizerincorporated therewith, depending on the inflammability desired.

It is also desirable to incorporate such compositions in a wet state forsake of safety and for more intimate mixing of the ingredients. Inselecting the oxygen delivering substance, I prefer the use of the lesshygroscopic materials, such as the nitrates of barium or potassium; thechlorate, chromate, dichromate or permanganate of potassium; metallicoxides, as the peroxides of manganese, lead or barium; etc.-In-selecting the fuel, I prefer the use of one or more materials, whosecombustion will take place, at a moderately fast rate, but withoutadvancing to detonation, when incorporated with the selected oxygendelivering substance and whose heat of oxidation is sufficiently highfor practical quantities, to effectively initiate a safety" primarydetonator composition, without being high enough to soften, melt orotherwise injure the confining medium, under the conditions of use.Typical fuel examples are tetryl; charcoal; naphthalene; selenium;trinitrotoluene; various picrates as ammonium picrate, etc.; varioussolid nitrocarbohydrates as nitrocotton, nitrostarch, nitrolactose,etc.; smokeless powder; and the like.

Various powdered metallic substances as sili con, magnesium, aluminum,ferro-silicon, and the like, may also be employed in varying quantities, but careful attention must be paid to the heat of combustion ofthe particular one selected, to make sure that the proportion used inthe composition will develop insufiicient heat, when employed as theignition medium, to injure the particular confining media used in thedetonator.

Powdered magnesium, for example, may be used only in proportions up toabout 10%, in conjunction with another tempering fuel of the type oftetryl (see composition C given above), for use as ignition mediaingilding metal shells of conventional thickness. Finally, if necessary toimprove the inflammability of the ignition media, I may add variousproportions of such materials as metallic sulphocyanates (as leadsulphocyanate), metallic hypophosphites (as lead hypophosphite) antimonysulphide, and the like, which serve as infiammability sensitizers.

' In adapting suitable types of inflammable materials as ignition media,in accordance with my invention, it is not only very desirable to useminimum amounts for the sake of economy and to minimize the reduction inclearance above the detonator charges in the shells, but also quiteadvisable to avoid excessive amounts for the most reliable functioningof the detonators. In general, the heights of column of pressed ignitionmedia are preferably no greater than about 4;. It is thereforepreferable to select a relatively fast burning ignition medium, smalleramounts of which may be used, than to select a relatively slow burningignition medium, much larger amounts of which are necessary to producethe heat required to effectively initiate the safety type of primarydetonator charges.

An additional reason for this preference is that the longer duration ofdefiagration, prior to the initiation of the primary charges, involvedwith larger amounts of .slower burning ignition media, are more apt toheat conventional types of detonator shells to sufiicientlyhigh-temperatures to pre-ignite the surrounding explosive charges-eventhough the shells are not actually penetrated or injured thereby.

In accordance with the above, I prefer inflammable compositions, of thegeneral type, represented by composition B, described above. CompositionB, I have found, consisting of an incorporated mixture of 20% potassiumchlorate, 40% ground smokeless powder, and 40% lead sulphocyanate, isquite suitable for ignition media, in accordance with my invention, forboth safety-fuse and electrically heated bridge-wire initiation;embodying many desirable properties. For example, it is notobjectionably hygroscopic, it. may be consistently ignited by theendspits of ordinary types of safety-fuse--eve'n in a pressed state thatwill resist being dislodged with reasonable amounts of handling, it maybe consistently ignited by means of conventional types of electricallyheated bridge-wires in contact therewith, and only small quantities(from about .04 gram to about .08 gram) arev required.

It will be understood that I recognize the possibility of usingespecially heavy confining media and/or of special materials, havinghigh heat resistances and/or low heat conductivities, to withstand theeffects of the hotter types of ignition media; the employment of whichis entirely within the scope of my invention. It will be also understoodthat I contemplate the ignition media, used in accordance with myinvention, being in various suitable forms, as for example: as loosepowders in contact with electrically heated bridge-wires; assuperimposed pressed charges to take the spits of safety-fuse; assuperimposed charges produced by introducing the inflammable compositioninto the detonators in a paste or liquid form and subsequentlysolidified, etc.

Further, it will be understood that my invention is applicable todetonators of any type, wherein "safety types of primary detonatorcompositions, as defined above, are employed. Within this scope areincluded both simple and compound detonators, whose primary detonatorcompositions consist of one or more essential ingredients, such as solidnitration products of polyhydric alcohols of the general formulaCnHn-2(OH) n, as nitromannite, nitrodulcite, nitroerythrite, and thelike, solid nitration products of disaccharides, as nitrolactose and thelike,

with or without various proportions of other solid explosives that arematerially less sensitive than mercury fulminate, lead azide and thelike, as tetryl, TNT, pentaerythritetetranitrate, nitrostarch, picricacid and the like. Compound detonators embodying my invention may alsoinclude base charges consisting of one or more solid explosives that arecompatible with the primary charges used therewith, such as tetryl, TNT,nitropentaerythrite, nitrolactose, nitrodulcite, nitromannite,nitrostarch, picric acid and like substances that are less sensitive tofriction and impact than mercury fulminate, lead azide,diazodinitrophenol, and the like.

Various means of firing detonators, embodying my invention, are alsocontemplated as, for example, conventional and unusual types ofsafety-fuses, conventional and unusual types of electrical media asbridge-wires, spark gaps, conventional electrically ignited pre-formedfuseheads or matches, etc.

Various materials may also be used for the of the ignition media.Whereas gilding metal is preferred, on account of its being non-sparkingand conventional for detonators, as well as 'entirely suitable inconventional thicknesses for various types of ignition media asillustrated above, other materials of various thicknesses may beemployed, if desired.

Having described my invention, what I claim l. A detonator including aconfined charge of a safety type of primary detonator composition, andan ignition medium for the said primary charge; the heat and pressuredeveloped by said ignition medium being incapable of prematurelyinjuring the confinement of the said primary charge prior to thedetonation thereof.

2. A detonator comprising, in combination, a metal shell having asuitable inside diameter for conventional types of safety-fuse or about.222 inch, a primary charge of a safety type of primary detonatorcomposition confined therein, an inner capsule for auxiliary confinementof the said primary charge, and placed upon the confined primary charge,an ignition medium consisting of an inflammable, deflagrating materialof such character and in such amount that the said ignition mediumdevelops sufficient heat to effectively initiate the said primaryexplosive charge but insufiicient heat to soften or melt the saidconfining shell or inner capsule and insufficient gas pressure toprematurely burst or injure the said confining shell or capsule prior tothe detonation of the said primary explosive charge.

3. A detonator as in claim 2, characterized by the ignition mediumthereof consisting of the fo1lowingfrom about .04 gram to about .08gram, pressed up to about 2600 lbs. per square inch, of a mixtureconsisting of about 40% ground smokeless powder, about 20% potassiumchlorate and about 40% lead sulphocyanate.

4. A detonator as in claim 2, characterized by the ignition mediumthereof consisting of the followingabout .4 gram, pressed up to about1300 lbs. per square inch, of a mixture consisting of about 74% seleniumdust and about 26% peroxide of barium.

5. A detonator as in claim 2, characterized by the ignition mediumthereof consisting of the following-from about .15 gram to about .25gram, pressed up to about 2600 lbs. per square inch, of a mixtureconsisting of about 40% barium nitrate, about 10% magnesium powder,about 25% tetryl and about 25% lead hypophosphite.

6. A compound detonator as in claim 21, whose base charge consists oftetryl and whose primary charge consists of nitromannite alone oradmixed with other solid explosives less sensitive to friction andimpact than mercury fulminate, lead azide and the like.

7. A detonator as in claim 2, whose primary charge consists ofnitromannite alone or admixed with other solid explosives less sensitiveto friction and impact than mercury fulminate, lead azide and the like.

8. A detonator as in claim 2, whose primary charge consists ofnitrodulcite alone or admixed with other solid explosives less sensitiveto friction and impact than mercury fulminate, lead azide and the like.

. primary charge consists of nitrolactose.

10. A compound detonator as in claim 21, whose base charge consists oftetryl and whose primary charge consists of a 50-50 mixture ofnitromannite and nitrolactose.

11. A detonator as in claim 2, whose primary charge consists of an -15%mixture of nitromannite and tetryl.

12. The method of initiating a detonator, including a primary charge ofa safety type of primary detonator composition comprising a solidnitration product of polyhydric alcohol of the general formulaCnHn+2(0H) n, and a confining medium for the said primary charge, whichcomprises superimposing an ignition medium on the said confined primarycharge, bringing about the ignition of the ignition medium so as toeifectively initiate the said primary charge; the composition and amountof the said ignition medium being so controlled in its development ofheat and pressure as to prevent premature injury of the said confiningmedium prior to the detonation of the .said primary charge.

13. A detonator comprising a shell, a primary safety charge in saidshell, 2. confining element for said charge in said shell, and anigniting medium for said charge; the character and amount of theigniting medium being such with respect to the strength of the shell andconfining means that said shell and confining means are completelyresistant as to impairment of the confinement of the primary chargeunder the heat and pressure developed within the shell up to the time ofdetonation of the primary charge.

14. In a detonator comprising a safety" type of primary detonator chargeand a confining means for the said primary charge, an inflammable,deflagrating ignition medium that evolves less heat and gas pressurethan that required to injure the said confining element within the timerequired for the said ignition medium to effect detonation of thesaidprimary charge.

15. A detonator comprising in combination a shell, 9. primary charge ofa safety type of primary detonator composition consisting of a. solidexplosive of the general formula CnHn+2(N03)n confined in said shell,and an ignition medium for the primary charge consisting of thefollowing-from about .04 gram to about .08 gram, pressed from zero up toabout 2600 pounds per square inch, of a mixture consisting ofapproximately 40% ground smokeless powder, approximately 20% potassiumchlorate and approximately 40% lead sulphocyanate.

16. A detonator comprising in combination a metal shell having asuitable inside diameter for conventional types of safety fuse of about.222 inch, a primary charge of a safety type of primary detonatorcomposition confined in said shell, and an ignition composition disposedoutw'ardly of said primary charge consisting of a mixture of groundsmokeless powder, potassium chlorate and lead sulphocyanate.

17. A detonator comprising a primary charge of a safety primarydetonator composition consisting of a solid explosive of the generalformula CnHn+2(NO3)n, a confining means for the said primary charge, andan ignition medium consisting of an inflammable deflagrating material of'such character and in such amount that the said ignition mediumdevelops suflicient heat to effectively initiate the primary chargewithout developingsufiicient heat and pressure to injure the saidconfining means prior to the detonation of the said primary detonatorcharge.

18. A detonator comprising a shell, a primary charge of the safety typeconfined therein, a confining capsule for the said primary charge withinthe shell and a hot flash composition of such material and such amountthat the flash delivered thereby is sufiiciently hot to effectdetonation of the primary charge but not hot enough, and the pressuregenerated thereby insuflicient to injure or dislodge the confining shelland capsule within the time required to effect detonation of the primarycharge.

19. A detonator comprising in combination, a confined primary explosivecharge that is free of any ingredient that is as sensitive to frictionand impact as mercury fulminate, lead azide or diazodinitrophenol, andan inflammable deflagrating medium for the effective initiation of the.said primary charge; the heat and pressure generated by said ignitionmedium being incapable of prematurely injuring the confinement of thesaid primary charge prior to the detonation of said primary charge.

20. A detonator comprising, in combination,

a primary explosive charge that is free of any ingredient that is assensitive to friction and no impact as mercury fulminatediazodinitrophenol or lead azide, a confining means for the said primarycharge, and an ignition medium for the effective initiation of the saidprimary charge consisting of a charge of inflammable deflagratingmaterial super-imposed upon the said primary detonator charge, the saidignition medium being of such character and in such amount that the heatand pressure produced by its deflagration are incapable of prematurelymelting or otherwise injuring the said confining means prior to thedetonation of the said primary charge.

21. A compound detonator comprising a shell, a base charge therein of anexplosive that is free of any ingredient that is as sensitive tofriction and impact as mercury fulminate diazodinitrophenol or leadazide, a primary charge of a "safety type of primary detonatorcomposition confined in said shell outwardly of the base charge, aconfining capsule within the shell and bearing upon said primary charge,and an ignition medium consisting of an inflammable deflagratingmaterial of such character and in such amount that the said ignitionmedium develops suflicient heat to efiectively initiate the said primaryexplosive charge but insufficient heat and pressure to prematurelysoften, melt, burst or injure either the confining shell or capsuleprior to the detonation of the said primary charge.

SYLVESTER B. LARGE.

